In recent years, higher integration, higher functionality, and higher density mounting of semiconductors widely used in electronic equipment, communication instruments, personal computers, and the like have been increasingly accelerated. Therefore, the demand for higher performance of a thermal expansion coefficient, drillability, heat resistance, flame retardancy, and the like in laminates for semiconductor plastic packages has increased more than ever before.
In addition to these, a reduction in the thermal expansion coefficient of the laminate in the planar direction has been strongly required, particularly in recent years. This is because, if the difference in thermal expansion coefficient between a semiconductor device and a printed wiring board for a semiconductor plastic package is large, when a thermal shock is applied, warpage occurs in the semiconductor plastic package due to the difference in the thermal expansion coefficient, and poor connection occurs between the semiconductor device and the printed wiring board for a semiconductor plastic package, and between the semiconductor plastic package and the mounted printed wiring board.
Conventionally, methods of relatively highly blending an inorganic filler in a resin composition in order to decrease the thermal expansion coefficient while satisfying various properties required of a laminate have been known (for example, see Patent Literatures 1 and 2). However, a problem of these methods is that the cured product of the resin composition is hard and brittle, and therefore, when a laminate obtained using this is drilled, the drillability is worsened, for example, the hole position precision decreases, the drill bit wears quickly and thus the frequency of the replacement of the drill bit increases, and the breakage of the drill bit is likely to occur.
On the other hand, as methods for improving the drillability of a laminate, methods of blending a molybdenum compound, such as zinc molybdate or calcium molybdate, in a resin composition have been known (for example, see Patent Literature 3).